The TargetBC project is funded by the Clean Air Fund under its 'superpollutants' initiative focussing on black carbon, and is being implemented between May 2025 and May 2027

Project partners (U.Aarhus, Denmark; University of Leeds/UK Meteorological Office, UK; CICERO, Norway; NILU, Norway; University of Stockholm, Sweden; AMAP Secretariat)  and associated partners (Environment and Climate Change Canada and University of Montreal, Quebec)

Aim and main activities: The project work  involves performing fixed-SST and fully-coupled Earth System Model (ESM) simulations, the results of which will be used to 'train' an emulator tool that can be used to investigate black carbon emissions reduction options to inform policy-making on climate responses. The (OpenSource) emulator development builds on a version applied in the AMAP 2021 SLCF assessment work, but with substantial improvements including the ability to run on the basis of emissions rather than air concentrations, and training the model using multi-model ESM results from five state-of-the-art ESMs (GISS-E2.1, NorESM2.0.6, UKESM1.1, CanESM5.1-PAM, and CESM2). 

Additional project components include inverse modelling using the FLEXPART CTM and observational data to validate source-receptor relationships.

The regional focus of the work is on the Arctic with a wider/global application on emission sources in Europe and Asia (India and China). 

Task: Delivering ESM simulation results to underpin the development and 'training' of the TargetBC emulator

Authors: Marianne T. Lund, Ulas Im, Cynthia Whaley, Steven Turnock, Zhihong Zhuo, Peter Langen;

Version: April 2026

As part of the TargetBC project, a set of ESM experiments have been designed, perturbing emissions of black carbon (BC) and sulfur dioxide (SO2) in different latitude bands and geographical regions. The following describes the experiment setup and output. This document also contains directions for accessing, using, and acknowledging the data (Section 4).

In addition to a year 2014 control simulation, simulations where emissions are perturbed individually in 4 broad latitude bands and 4 geographical regions were performed.  An additional experiment perturbing global shipping emissions is requested. Table 1 summarizes the experiments. Simulations have been performed with 5 models: GISS-E2.1, NorESM2.0.6, UKESM1.1, CanESM5.1-PAM, and CESM2. A brief overview of these models is provided in Appendix 1, including information about their treatment of aerosols and deposition of BC on snow. 

1.Experiment details: 

• Participating models were used in their CMIP6 configuration and all emissions and forcing data were as per CMIP6
• For the control and latitude band perturbations, both fixed SST (free running AMIP style) and ocean coupled simulations were requested
• For the geographical region perturbations only fixed SST simulations were requested
• Fixed SST simulations were run for between 30 and 45 years, using the last 20 for the estimation of  effective radiative forcing (ERF)
• Coupled simulations were run for 100 years, discarding as spin-up a model dependent number of years (see Table 2) 
• For all experiments, one realization/ensemble member was run 
• Models used their own default prescribed sea surface temperature or fSST runs (either year 2014 or climatology – see individual model details in Table 2)
• Models did not use a common restart file 

2. Emission perturbations were implemented as follows:

• All perturbations were 10x year 2014  CMIP6 emissions of BC and SO2, respectively, keeping everything else fixed in the control simulation configuration. [One model (GISS-E2.1) used a climatological mean of the biomass burning emissions as the basis for the 10x perturbation, the rest perturbed single year emissions. A preliminary analysis showed that 2014 did not stand out as an extreme biomass burning year, at least globally. ]
• For black carbon: 
  -  Latitude bands: all experiments are performed with the perturbation applied to land anthropogenic (i.e. no international shipping or aviation) plus biomass burning emissions  AND with the perturbation applied to land anthropogenic emissions only.
  - Geographical regions: the perturbation applied to only land anthropogenic 
• For sulfur dioxide: 
  - Latitude bands: perturbation applied to land anthropogenic emissions only. 
  - Geographical regions: perturbation applied to land anthropogenic emissions only
• The definition of the geographical regions follows those used in the HTAP3-OPNS experiments. The region mask file is available here.   

3. Model output request and file naming convention: 

The models were requested to output standard CMIP6 monthly mean variables. A complete list of requested variables is given in Appendix 2. 
For models who can do this, selected additional variables at daily resolution were requested: 
ta, trefht, prect, psl, fluxes (rsut, rsdt, rlut, rsds, rsus, rlds, rlus), concbc, od550aer, abs550aer, cl, clt

The naming of output files roughly follows the CMIP6 convention: 
<variable>_<timeres>_<modelname>_<experimentname>_<experiment_type> [optional:_<realization>_<model_grid>_<time_period>].nc
variable = CMIP6 name. timeres = mon or day. experiment: experiment short name from Table 1, experiment type: atm for fSST runs, cpl for coupled ocean runs. 

4. Data access and further use: 
Model output is stored in part on the Electronic Research Data Archive at Aarhus University (ERDA), with additional variables available from individual institutions storage facilities. Data will be made openly available once documented but is at present available for further analysis upon request. If using one or more data sets in a publication, we ask that you offer co-authorship to the people who designed and carried out the simulations. Contact points and people to include in further publications are for each model:
-    CanESM5.1-PAM: Cynthia Whaley 
-    GISS-E2.1: Ulas Im
-    NorESM2: Marianne T. Lund, Maura Dewey 
-    UKESM1.1: Steven Turnock 
-    CESM2: Zhihong Zhuo 
For questions related to ERDA: Ulas Im. 

A further OpenAccess archive will be established for model results datasets in connection with planned publications presenting project results.

We kindly ask that you acknowledge the TargetBC project in any use of these data, as follows:“This dataset was produced as part of the Clean Air Fund (CAF) project TargetBC”. 

 

Due to a scaling factor within the model being applied to CMIP6 configuration, he UKESM simulations are actually x20 biomass burning (emissions data should reflect this).